1. Field of the Invention
This invention relates generally to detecting objects imbedded in turbid media such as smoke, fog and water. This invention relates particularly to heterodyning optical signals to enhance a desired signal while averaging out scattered and ambient noise. Still more particularly this invention relates to a using heterodyne detection in a laser-line-scan system for increasing signal-to-noise and resolution in diverse applications such as mine hunting, diving, salvage and medical imaging.
2. Description of the Prior Art
The difficulties detecting objects imbedded in turbid media are well known. In laser-based systems, the primary causes of image degradation are the short range due to high extinction coefficients for turbid media and the large return of backscattered, forward-scattered, and ambient light into the detector washing out the signal. The scattering problem is reduced, but not eliminated by range-gating and line-scan systems.
The scattered light cannot be used to reconstruct high resolution images using conventional imaging techniques. The contrast of the image is further reduced as a result of light scattered by the turbid medium directly into the camera.